# US 12,112,507 B1 · Method and device for fast focusing by directly detecting target moments

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- Number: US 12,112,507 B1
- Document ID: US12112507B1
- Status: Granted
- Kind: B1
- Application number: 18/658,189
- Filed: 2024-05-08
- Granted: 2024-10-08
- Earliest claimed: 2024-01-22
- Assignees: Hefei Institutes of Physical Science, Chinese Academy of Sciences
- Applicants: Hefei Institutes of Physical Science, Chinese Academy of Sciences
- Inventors: Dongfeng Shi; Yingjian Wang; Yafeng Chen; Jian Huang; Huiling Chen
- Web page: https://patentgrep.com/patent/US12112507B1

## CPC

- G06T 7/80: Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
- G06T 7/60: Analysis of geometric attributes
- G06T 7/70: Determining position or orientation of objects or cameras (camera calibration G06T7/80)
- H04N 23/67: Focus control based on electronic image sensor signals
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

Provided are a method and a device for fast focusing by directly detecting target moments. The method includes: generating a setting modulation matrix and loading the modulation matrix to an optical modulator, receiving an optical signal emitted or transmitted by a target object at a current focusing position, and modulating, by the modulation matrix, the optical signal; acquiring a geometric moment value of the target object at the current focusing position according to the modulated optical signal; calculating a central moment; and a focusing position, obtained by refocusing, serving as the current focusing position, returning the optical signal of the target object that is received at the current focusing position and emitted or transmitted by the target object, comparing the central moment corresponding to the target object at all the focusing positions, and determining the focusing position that corresponds to the minimum central moment as the focusing position.

## Claims

### Claim 1

A method for fast focusing by directly detecting target moments, comprising:
generating a setting modulation matrix and loading the modulation matrix to an optical modulator, receiving an optical signal emitted or transmitted by a target object at a current focusing position, and modulating, by the modulation matrix, the optical signal;
acquiring a geometric moment value of the target object at the current focusing position according to the modulated optical signal;
calculating a central moment, that corresponds to the target object at the current focusing position, according to the geometric moment value; and
serving a focusing position obtained by refocusing as the current focusing position, returning the optical signal of the target object that is received at the current focusing position and emitted or transmitted by the target object until the central moment corresponding to the target object at all focusing positions is obtained, comparing the central moment corresponding to the target object at all the focusing positions, and determining the focusing position that corresponds to the minimum central moment as the focusing position.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the acquiring the geometric moment value of the target object at the current focusing position according to the modulated optical signal comprises:
using a single-pixel detector to acquire the geometric moment value of the target object at the current focusing position according to the modulated optical signal.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the acquiring the geometric moment value of the target object at the current focusing position according to the modulated optical signal comprises:
determining a two-dimensional function Si(x,y) that corresponds to the i modulation matrix; and
modulating the optical signal according to the two-dimensional function Si(x,y) to obtain the optical information intensity value Ii corresponding to i, which is equivalent to the geometric moment value corresponding to i.

### Claim 4 (depends on 3)

The method according to claim 3, wherein the setting modulation matrix comprises:
a modulation matrix M1, which is a two-dimensional matrix, and an element value of each position therein is 1;
a modulation matrix M2, which is a two-dimensional matrix, and an element value of each line therein is equal to a line sequence number thereof; and
a modulation matrix M3, which is a two-dimensional matrix, and an element value of each line therein is equal to the square of the line sequence number thereof.

### Claim 5 (depends on 4)

The method according to claim 4, wherein the determining the two-dimensional function Si(x,y) that corresponds to the i modulation matrix comprises:
determining the two-dimensional functions S1(x,y), S2(x,y) and S3(x,y) that correspond to the modulation matrices M1, M2 and M3, and separately meeting:
S1(x,y)=1
S2(x,y)=x
S3(x,y)=x2
an abscissa and an ordinate of a coordinate system where the two-dimensional functions S1(x,y),S2(x,y) and S3(x,y) are located correspond to row directions and column directions of the modulation matrices M1, M2 and M3, respectively:
the modulating the optical signal according to the two-dimensional function Si(x,y) to obtain the optical information intensity value Ii corresponding to i, which is equivalent to the geometric moment value corresponding to i comprises:
the corresponding optical information intensity value Ii that is acquired by modulating the optical signal based on the two-dimensional functions S1(x,y),S2(x,y) and S3(x,y) is denoted as:
Ii=Σx,yƒ(x,y)Si(x,y);
in the formula, i value is 1, 2, 3, and ƒ(x,y) is a two-dimensional distribution function of a target object image at the current focusing position; and
the detected optical intensity values I1, I2 and I3 are equivalent to geometric moment values m00, m10 and m20, respectively.

### Claim 6

A device for fast focusing by directly detecting target moments, comprising:
a modulation module configured to generate a setting modulation matrix and to receive an optical signal emitted or transmitted by a target object at different focusing positions, and the modulation matrix modulates the optical signal;
a geometric moment value acquisition module configured to acquire a geometric moment value of the target object at the different focusing positions according to the detected and modulated optical signal;
a central moment value acquisition module configured to receive the geometric moment value output by the geometric moment value acquisition module and to calculate a central moment corresponding to the target object at the different focusing positions; and
a focusing position determination module configured to compare the central moment corresponding to the target object at all the focusing positions, and the focusing position that corresponds to the minimum central moment is determined as the focusing position.

### Claim 7 (depends on 6)

The device according to claim 6, wherein the modulation module comprises a two-dimensional matrix generation unit and an optical modulator, the two-dimensional matrix generation unit generates a plurality of modulation matrices, and the optical modulator uses different modulation matrices sequentially and periodically to modulate the optical signal.

### Claim 8 (depends on 7)

The device according to claim 7, wherein the optical modulator comprises a plurality of micro-mirrors presenting an array distribution, and each element value in the modulation matrices corresponds to an unique micro-mirror.

### Claim 9 (depends on 1)

A non-transitory computer-readable storage medium, wherein the medium stores a computer program, and while the computer program runs, the method for fast focusing by directly detecting target moments according to claim 1 is implemented.

### Claim 10 (depends on 1)

A computer device, comprising a processor and a storage medium, wherein the storage medium stores a computer program, and the processor reads and runs the computer program from the storage medium to execute the method for fast focusing by directly detecting target moments according to claim 1.